x11vnc: move recipe from oe-core

x11vnc will be configured to use the external libvncserver which is
added to meta-oe. Since oe-core recipes should not depend on meta-oe
recipes, we move x11vnc to meta-oe.

Signed-off-by: Ioan-Adrian Ratiu <adrian.ratiu@ni.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>